bgpd: replace ipv4-mapped ipv6 at update forwarding

Replace IPv4-mapped IPv6 at update forwarding because the peer may not be able to create a route with the IPv4-mapped IPv6. Signed-off-by: Louis Scalbert <[email protected]>
FRRouting · Oct 17, 2024 · 8859327 · 8859327
1 parent 9d6a779
commit 8859327
Showing 1 changed file with 15 additions and 0 deletions.
diff --git a/bgpd/bgp_updgrp_packet.c b/bgpd/bgp_updgrp_packet.c
@@ -508,6 +508,9 @@ struct stream *bpacket_reformat_for_peer(struct bpacket *pkt,
 				gnh_modified = 1;
 			}
 		} else if (IN6_IS_ADDR_UNSPECIFIED(&v6nhglobal)) {
+			/* the UPDATE is originating from the local router.
+			 * Build the global nexthop.
+			 */
 			mod_v6nhg = &peer->nexthop.v6_global;
 			gnh_modified = 1;
 		} else if ((peer->sort == BGP_PEER_EBGP)
@@ -521,6 +524,14 @@ struct stream *bpacket_reformat_for_peer(struct bpacket *pkt,
 			 */
 			mod_v6nhg = &peer->nexthop.v6_global;
 			gnh_modified = 1;
+		} else if (IS_MAPPED_IPV6(&v6nhglobal) &&
+			   !IN6_IS_ADDR_LINKLOCAL(&peer->nexthop.v6_global)) {
+			/* prefer a IPv6 native global address over
+			 * an IPv4-mapped IPv6 address as nexthop when
+			 * forwarding UPDATEs.
+			 */
+			mod_v6nhg = &peer->nexthop.v6_global;
+			gnh_modified = 1;
 		}
 
 		if (!peer->conf_if && peer->nexthop.v4.s_addr != INADDR_ANY &&
@@ -533,6 +544,10 @@ struct stream *bpacket_reformat_for_peer(struct bpacket *pkt,
 		}
 
 		if (IS_MAPPED_IPV6(&peer->nexthop.v6_global)) {
+			/* If the interface to the peer has no global IPv6
+			 * address, replace the nexthop in UPDATE with
+			 * the IPv4-mapped IPv6 address if any.
+			 */
 			mod_v6nhg = &peer->nexthop.v6_global;
 			gnh_modified = 1;
 		}